Massachusetts Institute of Technology (MIT) reports that its MIT Energy Initiative (MITEI) researchers have found that strategies to limit climate change rely on overly optimistic assumptions about removing carbon dioxide using direct air capture (DAC). The MITEI team however says work on DAC should continue, because it can play a role.
DAC coupled with CO2 storage in geologic formations keeps the carbon dioxide kept out of the atmosphere “essentially permanently” (unlike sequestering it in trees) the report says. MITIE investigated whether current plans that rely on DAC would be effective in stabilizing the climate. In a paper published in the journal One Earth they found three unavoidable engineering challenges that together mean high costs for DAC.
First was the low concentration of carbon dioxide in the air, which meant processing about 1.8 million cubic meters of air across sorbent to remove a single tonne of carbon dioxide.
Second was the energy required to move large quantities of air across a sorbent, with most proposed processes requiring at least 1.2 MWh of electricity for each tonne of carbon dioxide removed. DAC would be competing with industry and other users for that and using waste heat from nearby industry “may be more wishful thinking than reality”.
Finally, siting DAC units will be complex. They have to be close to energy sources and to storage sites or pipelines. In addition, meteorological conditions must be acceptable and the DAC units will have to be far enough apart not to affect each other’s performance.
The cost of meeting these challenges was often underestimated, the MIT report says.
Nevertheless, the researchers recommend that work to develop DAC continue “because it may be needed for meeting net-zero emissions goals, especially given the current pace of emissions.”
See the full story and link to the original paper here